1813.] Oxymuriatic Acid ivith Lime, 7 



there were 20 grains of lime in solution. This small difference 

 arises, perhaps, from the errors of the proportions; or, perhaps, 

 from the liquid containing a very small portion of muriate of 

 lime. This last idea was tried by saturating one-fifth of the 

 liquid (I '041) by test muriatic acid, and expelling the oxymu- 

 riatic acid, as related in my former paper; but it was found that 

 the lime required as much acid as was sufficient to saturate it, or 

 so nearly that quantity that the difference was scarcely appre- 

 ciable. 



Since the former essay was written, I have found another 

 method of determining the quantity of oxymuriatic acid in any 

 specimen of oxymuriate; it is to dissolve a known weight of the 

 oxy muriate in. a small portion of water; then put the liquid into 

 a graduated tube over mercury, and discharge the gas by an 

 acid; it may thus be measured, and the quantity retained by the 

 liquid may be estimated at twice the bulk of the liquid nearly. 

 [See New System of' Chemical Philosophy, p. 298.] Three 

 grains of the dry oxymuriate above give, when dissolved in 30 of 

 water, and 20 grains of dilute acid are added, 1 70 measures of 

 gas over 50 of watery solution, which last may be presumed to 

 retain 90 more. Hence the total gas may be estimated at 260 

 measures, which, of the sp. gr. 234, would give '72 grain for 3, 

 .equal to 24 per cent, of acid in the salt. The gas, I find, may 

 be kept in the tube under these circumstances for a week, with- 

 out losing more than 40 or 50 measures of its volume; so that its 

 combination with mercury is slow, if not agitated. Upon the 

 whole, however, I prefer the green sulphate test for precision. 



As nothing was in the salt but oxymuriatic acid, lime, and 

 water, we have its constitution as under : — 



23 oxym. acid 

 3S lime 

 39 water 



100 



But as the hydrate of lime at first had a minimum of water, 

 which is known to be J- of its weight, it could only be 13 grains: 

 whence, then, were derived the other 26 grains of water? This 

 is an important question ; especially as the specimen in my 

 former paper was found to contain an equal, or greater, quantity 

 of water (<12) per cent. 



Expc-r. 3. — Suspecting that more water was found in the 

 oxymuriate of lime than was essential to its existence, I attempted 

 to distil the surplus water off by a gentle heat. A small portion 

 of the salt was put into one end of a glass tube, and a gentle 

 beat applied ; water soon dropped from the cool cud; it trailed 



